1. Field of the Invention
The present invention relates to a ceramic structure, more specifically, to a ceramic structure including a metallic body therein and, also, relates to a production process thereof.
2. Description of the Prior Art
There are several problems with conventional ceramic structures including metallic bodies. When the ceramic portion is formed around the metallic body in contact thereto, it tends to crack and break when the whole ceramic structure is subjected to a high temperature, especially when the metallic body is heated to a temperature higher than that of the ceramic portion. This is a result of the large difference between the thermal coefficients of expansion of the metal and the ceramic. The metallic body expands more than the space surrounded it and causes strain in the ceramic structure.
When the ceramic portion is formed around the metallic body with a large cavity provided therebetween to absorb the difference in the thermal expansion, the metallic body is not stably supported and will move around considerably, therefore, may not be properly retained in the resultant ceramic structure. This is especially true when the ceramic structure is used under a vibrating condition. Furthermore, when the metallic body is a heater for heating the ceramic structure, larger thermal resistance is caused by the large cavity between the metallic heater and the ceramic portion, reducing the thermal conductivity to the ceramic portion. Thus, the heater must be operated at much higher temperatures than ordinarily necessary in order to satisfactorily heat the ceramic structure. This results in burnout of the heater element when the ceramic structure should be heated to an extremely high temperature and in wasteful power consumption.